Dr. Stephen Gregory Raymond Barnard has over 13 years’ experience as a Radiation Protection Scientist at the UK Health Security Agency (UKHSA) and its predecessors. As head of the Cytogenetics Group and the Chromosome Dosimetry Service, his main field of research is radiation biodosimetry, using cytogenetic (cellular and chromosomal) effects of ionising radiation to estimate individual doses. The service is further underpinned by his and his colleagues’ studies into the cytogenetic effects of ionising radiation and statistical methods to support research and development, and he also has an interest in wider radiation protection, particularly whole-body radiation effects and radiation cataractogenesis. He is an experienced laboratory cytogeneticist particularly interested in early radiation-induced DNA damage and repair using response markers including ƴH2AX and 53BP1. He is part of a team of scientists carrying out biological dosimetry in the laboratory and its subsequent analysis. He has been instrumental in carrying out UKHSA’s work on a number of recent projects, taking responsibility for UKHSA’s gamma-H2AX assay work for MULTIBIODOSE, EU FP7 RENEB, and the current NIH CMCR RTGene and NIHR HPRU projects focused on biomarkers of exposure and effect for radiotherapy patients. He gained his PhD investigating early lens changes in response to ionising radiation, leading to radiation-induced cataracts, in association with Durham University.